The present invention relates to a saw guide which permits a cut to be made in a material at a desired angular orientation. More particularly, the present invention relates to a saw guide for controlling the resection of an upper part of a human tibia bone to prepare the bone for placement of the tibial portion of a knee prosthesis. The present invention permits a cut or resection to be made at a desired angular orientation, with the angular orientation being adjustable to meet the needs of the patient.
As a part of the surgical procedure for the implant of a knee prosthesis, the upper or proximal portion of the human tibia bone must normally be resected. This resection is necessary both to remove the damaged portion of the tibial joint, and to prepare a surface for placement of the tibial portion of the knee prosthesis. As will be understood, it is of vital importance to prepare the surface of the tibia that is to receive the component as accurately as possible. Accurate orientation of the tibial surface is critical because, in such a surgical procedure, the surgeons performing the operation are attempting to duplicate as closely as possible the function of the normal human knee. Thus, proper alignment of the artificial prosthesis is necessary to permit the artificial knee to appear normal, and to function in a normal manner. Because the anatomy and configuration of individual knees differs considerably between individuals, it would be highly desirable to be able to select an orientation of the tibial surface at the time of the resection to closely duplicate the orientation and configuration of the opposite or contralateral side of the patient.
Conventional tibial resection guides are generally placed external to the tibia bone and generally provide for only one angular orientation of the cut and are bulky in size. Thus, it is generally not possible with conventional tibial resection guides to select the angle at which the tibial resection is performed without changing the tibial resection guide to a different guide with a different angular orientation. Thus, conventional tibial resection guides are limited in that, should the surgeon decide that a non-standard angular orientation is desirable to suit the needs of the particular patient, such an angular orientation may be impossible, or difficult to achieve because of the inability of the conventional tibial resection guide to be adjusted to provide such a desired angular orientation.
It is therefore one object of the present invention to provide a tibial cutting guide which permits adjustment and selection of the proper angular orientation of the tibial surface to be formed during the resection procedure.
Another object of the present invention is to provide a tibial cutting guide which can be adjusted to different angular orientations in more than one plane.
Yet another object of the present invention is to provide a tibial cutting guide in which the depth of the cut of the proximal portion of the tibia can be easily selected so that only the minimum amount of bone needs to be resected to prepare the tibial surface.
According to the present invention, an apparatus for preparing a proximal surface of a human tibia bone to receive a tibial portion of a knee prosthesis is provided. The tibia bone has an anterior-posterior axis, a medial-lateral axis, and a central longitudinal (or anatomic) axis. The apparatus includes means for establishing a first axis that is generally parallel to the central longitudinal (anatomic) axis of the tibia bone. The apparatus also includes means for guiding a cutting blade into cutting engagement with a proximal portion of the tibia bone. Means for selectively adjusting the position of the guiding means along a first axis is provided as well as means for angularly orienting the guiding means with respect to a first plane that is perpendicular to the first axis. This allows the guiding means to be properly positioned adjacent the proximal portion of the tibia bone to permit a portion of the bone to be resected to receive the tibia portion of the knee prosthesis.
One feature of the foregoing structure is that means are provided for selectively adjusting the position of the guiding means along the first axis. One advantage of this feature is that, by permitting adjustment of the guiding means along the first axis, the depth of the cut to be made in the proximal portion of the bone can be adjusted so that the minimum amount of bone can be resected.
Another feature of the foregoing structure is that means for angularly orienting the guiding means with respect to a first plane that is perpendicular to the first axis is provided. By permitting selective angular orientation of the guiding means with respect to the first plane, the angular orientation of the cut to be made in the knee, and consequently the angular orientation of the resected tibial surface can be adjusted and selected according to the anatomical requirements of the individual patient at the time of the resection.
In preferred embodiments of the present invention, the adjusting means includes a first height adjusting device that is mounted on the end of an elongated rod that is adapted to be inserted into the medullary canal in the tibia bone. One feature of the foregoing structure is that, by utilizing an elongated rod that fits into the medullary canal within the tibia bone, stabilization and alignment of the apparatus is provided with reference to the tibia bone itself. One advantage of this feature is that more accurate stabilization and alignment of the device is provided.
Also in preferred embodiments of the present invention, the orienting means includes a pivot device that is cantilevered away from the first height adjusting device and that is attached to the guiding means to permit limited pivotal movement around a second axis that is generally parallel to the medial-lateral axis of the tibia bone. This limited pivotal movement about the second axis permits adjustment of the angular orientation of the guiding means relative to a third axis that is generally parallel to the anterior-posterior axis of the bone. One feature of the foregoing structure is that a pivot device is provided that is capable of rotation about an axis to permit selective adjustment of the angular orientation of the guiding means. One advantage of this feature is that the angular orientation of the guiding means, and consequently the angular orientation of the cut that is to be made in the tibia bone can be selectively adjusted to meet the requirements of the individual patient at the time the cut is to be made and/or to accommodate different surgical techniques, i.e. revision, total knee replacement, osteotomies, etc.
Thus, the present invention provides a tibial cutting guide which permits the angular orientation of the cut to be adjusted to meet the requirements of the patient. The angular orientation of the cutting guide, and consequently the angular orientation of the tibial surface after the bone has been resected, can be changed along two planes, which greatly increases the different angular combinations available to the surgeon. These angular combinations can be chosen by the surgeon while the invention is in place on the patient. Thus, it is not necessary to select differently oriented cutting guides to change the angular orientation of the cut.
Additional objects, features, and advantages of the present invention will be apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.